The present invention relates to a new class of polyols useful in the production of rigid polyurethane foams.
Several polyols are known and used in the art for the production of rigid polyurethane foams. In the area of polyols used for the so-called spray foams, those of the type disclosed in U.S. Pat. Nos. 3,297,597 and 4,137,265 have been particularly successful. In general, polyols of this type are prepared by alkoxylating the Mannich reaction product of a phenolic compound, an alkanolamine and formaldehyde. Similar polyols are described in U.S. Pat. No. 3,671,470.
It is further known to prepare polyols by alkoxylating a resole prepared by reacting a phenolic compound, urea (or melamine or dicyandiamide) and formaldehyde (see, e.g., U.S. Pat. No. 4,036,790). It has also been suggested to blend the resultant urea-modified resole based polyol with a Mannich based polyol of the type described in the above-noted U.S. Pat. Nos. 3,297,597 and 4,137,265 (see, col. 3, lines 15-19 of U.S. Pat. No. 4,036,790).
Finally, it is known to produce polyols by alkoxylating a condensation product of an aromatic amine, a phenolic compound and formaldehyde (see U.S. Pat. No. 3,222,305).
Although the polyols noted above have met with success, they suffer from several disadvantages. In the case of the Mannich based polyols and depending upon the molar ratios and the structures of the reactants, the Mannich reaction product (i.e., prior to alkoxylation) may not be stable at room temperature and upon sitting at room temperature undergoes further reaction. Such reaction products will be stable if the ortho and para positions of the phenolic nucleus are substituted with non-reactive groups, unless one of the phenolic ring positions is occupied with a methylol group. In addition, para-or ortho-substituted phenols (e.g., p-nonyl phenol), when reacted with adequate quantities of formaldehyde and an amine will form a structure which should be stable. The alkoxylated polyols have good shelf-life stability, however, the spray foams derived from such polyols do not exhibit entirely satisfactory dimensional stability.